Focal adhesion kinase is required for CXCL12-induced chemotactic and pro-adhesive responses in hematopoietic precursor cells

Abstract

Hematopoietic stem/progenitor cells (HSC/P) reside in the bone marrow in distinct anatomic locations (niches) to receive growth, survival and differentiation signals. HSC/P localization and migration between niches depend on cell-cell and cell-matrix interactions, which result from the cooperation of cytokines, chemokines and adhesion molecules. The CXCL12-CXCR4 pathway, in particular, is essential for myelopoiesis and B lymphopoiesis but the molecular mechanisms of CXCL12 action remain unclear. We previously noted a strong correlation between prolonged CXCL12-mediated focal adhesion kinase (FAK) phosphorylation and sustained pro-adhesive responses in progenitor B cells, but not in mature B cells. Although FAK has been well studied in adherent fibroblasts, its function in hematopoietic cells is not defined. We used two independent approaches to reduce FAK expression in (human and mouse) progenitor cells. RNA interference (RNAi)-mediated FAK silencing abolished CXCL12-induced responses in human pro-B leukemia, REH cells. FAK-deficient REH cells also demonstrated reduced CXCL12-induced activation of the GTPase Rap1, suggesting the importance of FAK in CXCL12-mediated integrin activation. Moreover, in FAK flox/flox hematopoietic precursor cells, Cre-mediated FAK deletion resulted in impaired CXCL12-induced chemotaxis. These studies suggest that FAK may function as a key intermediary in signaling pathways controlling hematopoietic cell lodgment and lineage development.

β-Arrestin1 and Signal-transducing Adaptor Molecule 1 (STAM1) Cooperate to Promote Focal Adhesion Kinase Autophosphorylation and Chemotaxis via the Chemokine Receptor CXCR4

“…1). Our data are also consistent with other studies that have shown that ␤-arrestins (12, 13) and FAK (32) are involved in CXCR4-promoted cell migration. Here, we establish that STAM1 is also required.…”

“…The ␤-Arrestin1⅐STAM1 Complex Regulates FAK Autophosphorylation-Next, we set out to identify the signaling pathway by which the ␤-arrestin1⅐STAM1 complex mediates chemotaxis. We focused on FAK, a non-receptor tyrosine kinase involved in CXCR4-dependent chemotaxis of hematopoietic precursor cells (32,33). First, we determined whether FAK is necessary for CXCR4-promoted chemotaxis of HeLa cells.…”

“…Next, we examined FAK activation by immunoblotting for the phosphorylation status of tyrosine residue 397 (Tyr-397), an amino acid residue that is triggered by several stimuli to be autophosphorylated (34,35), including CXCL12 (32,36). In cells expressing ␤Arr1 or STAM1(296 -380), CXCL12-induced phosphorylation of FAK at Tyr-397 was significantly attenuated compared with control (Fig.…”

Culturing of Human Mesenchymal Stem Cells as Three-dimensional Aggregates Induces Functional Expression of CXCR4 That Regulates Adhesion to Endothelial Cells

“…The tips of F-actin filaments are the sites of attachment of focal adhesion complexes. The activation of focal adhesion kinase by SDF-1 plays an important role in adhesion of hematopoietic precursor cells (47) and results in cytoskeleton rearrangements (33,47,48). Association of CXCR4 with the tips of F-actin filaments correlates with the reported stimulation of focal adhesion kinase by SDF-1 and suggests that the receptor might be a part of large macromolecular complexes assembled at the points of focal adhesion.…”

B Cell Receptor-induced Phosphorylation of Pyk2 and Focal Adhesion Kinase Involves Integrins and the Rap GTPases and Is Required for B Cell Spreading

“…FAK is involved in the chemokine-induced adhesion of B cell progenitors (34), and Pyk2 is required for chemokine-induced migration of mature B cells (25). However, the role of these kinases in BCR-and integrin-induced B cell spreading has not been investigated, and the signaling pathways that link the BCR and integrins to tyrosine phosphorylation of Pyk2 and FAK have not been elucidated.…”